The present invention relates to umbrellas, and more particularly, to an umbrella which vents air from its lower concave surface to the upper convex surface. Such a design helps to minimize or prevent damage to the umbrella due to air blasts and particularly, prevents or minimizes annoying umbrella inversion which may occur when the concave side of the umbrella is subjected to a blast of air.
Various umbrella designs, and in particular designs for minimizing the effects of gusts of wind on umbrellas are known. For example, U.S. Pat. No. 3,456,661 to Fairly discloses an umbrella having an upper umbrella covering comprising a plurality of flaps which are disposed over a central opening at the top of the lower umbrella covering. The flaps comprise a plurality of gores secured at their radial edges to the lower umbrella covering along lines defined by radially depending ribs. The gores have dimensions wider than the width between those ribs and taper with increasingly greater width than the width between those ribs. The gores of the Farley design umbrella are accordingly loose fitting and therefore present problems themselves in catching the wind and in presenting a non-traditional umbrella appearance.
U.S. Pat. No. 4,979,534 to Johnston et al. discloses a self described windproof umbrella having a plurality of holes in a first lower umbrella surface and having an overlying smaller umbrella surface which is secured by elastic bands to the ends of the ribs of the umbrella structure. The elastic bands are unattractive and subject to damage. Furthermore, these elastic bands may actually cause umbrella inversion to occur.
Other umbrella designs of interest include U.S. Pat. Nos. 617,415 to Eatman, 3,557,809 to Vasquez, 3,863,660 to Glaeser and 3,960,162 to Noel, Austrian Patent 106,457, U.S. Pat. No. 3,032,047 to Wendorf, French Patent No. 817,056, French Patent No. 1,284,022 and U.S. Pat. No. 1,031,974 to Thomas.
There is a need for an improved umbrella of simple, sturdy design which allows air due to wind impinging on the concave undersurface of the umbrella to escape to minimize the effects of the wind on the umbrella. As is known, a common effect of gusts of wind is an annoying inversion of the umbrella whereby the desired umbrella configuration comprising an upper convex surface and a lower concave surface inverts. In some situations, the wind can also damage the umbrella and cause it to be hurled out of the hands of a holder.